Shillong Lajong were Monday relegated from the I-League after they suffered a 1-4 defeat at the hands of former champions Aizawl FC in their penultimate round match in Aizawl.
Lajong remained stuck at the bottom of the 11-team I-League with 11 points from 19 matches.
Even if they beat Mohun Bagan at home on Saturday in their final match, Lajong are certain to end at the last place as their immediate better-placed side Gokulam Kerala are currently on 17 points from 19 matches.
The second half also saw Aizawl having more possession and Mapuia's entry in the 64th minute brought even more drive in the Aizawl attack.
Isak had a good chance to score in the 70th minute when the ball fell favourably for him near the top of the box but his volley went well over.
Mapuia missed a golden chance to double the lead for Aizawl in the 76th minute but keeper Chalieu did well to thwart the attempt from a one-on-one situation. But, he achieved his goal in the 81st minute.
It was Isak's delivery into the box from the right, which fell invitingly for Mapuia who made no mistake to head home.
The third goal came two minutes later as a Kenstar backpass to Chalieu went horribly wrong for the keeper and the Liberian poacher Kromah made him pay. It was Kromah's eighth goal of the 12th I-League season.
Isak finally got a well-deserved goal for himself. After a brilliant solo run along the box, he unleashed from the top of the box to bulge the Lajong net with a minute left in the regulation time.
Lajong's first shot on target was affected seconds later by Samuel Lalmuanpuia and they finally had something to show in the third minute of injury time. Substitute Donbok broke away from his marker inside the box on the left, following a lovely ball from Sheen, to send past Aizawl goalkeeper Gurpreet into the left corner.
